Emergency workers went door-to-door Thursday urging residents to leave their homes before floodwaters from the Blanco River converged on the San Marcos River to inundate the region.

“We’re anticipating some serious flooding,” the AP reported San Marcos police Chief Howard Williams as saying. “We’ve been trying to get ahead of the game, getting as many people out of these low-lying areas as they can.”

“I think it’s a good idea,” said Tara Dudzik, a National Weather Service meteorologist in Indiana. “Winds of up to 60 mph, and lightning — those are the main threats we’d be concerned about.”

City officials in Indianapolis and Muncie, Ind., said they have postponed trick-or-treating. To the north, Toledo is among 30 cities in Ohio that have put off the annual hunt for candy until as late as Sunday, Reuters said.

Of course, there is little authorities can do to stop the foolhardy. In Cincinnati and Nashville, where trick-or-treating has not been postponed, officials are urging caution.